Air conditioning system

ABSTRACT

An air conditioning system includes a refrigerant circuit, a heat exchanger, a shutoff valve, and a refrigerant leakage sensor. The refrigerant circuit includes a first part and a second part. The heat exchanger is provided in the first part and exchanges heat between a refrigerant and air in an air conditioning target space. The shutoff valve is provided in the refrigerant circuit and shuts off communication between the first part and the second part. The refrigerant leakage sensor detects that refrigerant concentration is within a first range and detects the refrigerant leaked from the first part. The shutoff valve is placed to set the refrigerant concentration in the air conditioning target space within a second range larger than the first range, when it is assumed that all the refrigerant present in the first part has leaked to the air conditioning target space.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of PCT International Application No.PCT/2020/043893, filed on Nov. 25, 2020, which claims priority under 35U.S.C. 119(a) to Patent Application No. 2019-217391, filed in Japan onNov. 29, 2019, all of which are hereby expressly incorporated byreference into the present application.

TECHNICAL FIELD

The present disclosure relates to an air conditioning system.

BACKGROUND ART

Patent Literature 1 (Japanese Laid-Open Patent Application No.2019-45129) discloses an air conditioning system in which a shutoffvalve is connected to the outside of a utilization-side unit. Theshutoff valve is a part to be closed when a refrigerant leakage isdetected, and shuts off the flow between a heat source-side unit and theutilization-side unit to prevent all the refrigerant filled in arefrigerant circuit of the air conditioning system from leaking.

SUMMARY

An air conditioning system of a first aspect includes a refrigerantcircuit, a heat exchanger, a shutoff valve, and a refrigerant leakagesensor. The refrigerant circuit includes a first part and a second part.The heat exchanger is provided in the first part, and cools or heats airin an air conditioning target space by exchanging heat between arefrigerant and the air in the air conditioning target space. Theshutoff valve is provided in the refrigerant circuit and shuts offcommunication between the first part and the second part. Therefrigerant leakage sensor detects the refrigerant leaked from the firstpart. The refrigerant leakage sensor detects that refrigerantconcentration is within a first range. The shutoff valve is placed toset the refrigerant concentration in the air conditioning target spacewithin a second range larger than the first range, when it is assumedthat all the refrigerant present in the first part has leaked to the airconditioning target space.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing a schematic configuration of an airconditioning system as one embodiment of a refrigerant cycle device.

FIG. 2 is a control block diagram of the air conditioning system.

FIG. 3 is a control flowchart when a refrigerant leaks

FIG. 4 is a schematic configuration diagram of the air conditioningsystem according to Modification A.

FIG. 5 is a schematic configuration diagram of the air conditioningsystem according to Modification B.

FIG. 6 is a schematic configuration diagram of the air conditioningsystem according to Modification E.

DESCRIPTION OF EMBODIMENT

With reference to the drawings, an air conditioning system 100 accordingto one embodiment of the present disclosure will be described below.

(1) Overall Configuration

(1-1) Air Conditioning System

The outline of the air conditioning system 100 including an airconditioning apparatus 1 according to one embodiment will be describedwith reference to FIG. 1. FIG. 1 is a schematic configuration diagram ofthe air conditioning system 100. The air conditioning apparatus 1 of theair conditioning system 100 is an apparatus that performs vaporcompression refrigeration cycle and cools and heats air conditioningtarget space. The air conditioning target space is, for example, anoffice or a living room in a house. In the present embodiment, the airconditioning apparatus 1 is an apparatus that can both cool and heat theair conditioning target space. However, the air conditioning apparatus 1of the present disclosure is not limited to the air conditioningapparatus capable of both cooling and heating, and may be, for example,an apparatus capable of only cooling.

The air conditioning apparatus 1 of the air conditioning system 100mainly includes a heat source-side unit 2, a plurality ofutilization-side units 3 a, 3 b, and 3 c, a first connection flow path21, a second connection flow path 22, and a control unit 19 (see FIG.2). The plurality of utilization-side units 3 a, 3 b, and 3 c isconnected in parallel to the heat source-side unit 2. The firstconnection flow path 21 and the second connection flow path 22 connectthe heat source-side unit 2 to the utilization-side units 3 a, 3 b, and3 c via a shutoff valve 70. The first connection flow path 21 and thesecond connection flow path 22 are laid at an installation site of theair conditioning apparatus 1. The pipe diameter and the pipe length ofthe first connection flow path 21 and the second connection flow path 22are selected according to the design specification and the installationenvironment. The control unit 19 controls the heat source-side unit 2,the utilization-side units 3 a, 3 b, and 3 c, and the shutoff valve 70.A vapor compression refrigerant circuit 10 of the air conditioningapparatus 1 is configured by connecting a heat source-side refrigerantflow path 14 of the heat source-side unit 2 to utilization-siderefrigerant flow paths 13 a, 13 b, and 13 c of the utilization-sideunits 3 a, 3 b, and 3 c by the first connection flow path 21 and thesecond connection flow path 22 via the shutoff valve 70. The heatsource-side refrigerant flow path 14 is a refrigerant flow path providedinside the heat source-side unit 2. The utilization-side refrigerantflow paths 13 a, 13 b, and 13 c are refrigerant flow paths providedinside the utilization-side units 3 a, 3 b, and 3 c, respectively. Thefirst connection flow path 21 includes utilization-side first connectionflow paths 21 aa, 21 ab, and 21 ac and a heat source-side firstconnection flow path 21 b. As shown in FIG. 1, the utilization-sidefirst connection flow paths 21 aa, 21 ab, and 21 ac and the heatsource-side first connection flow path 21 b are divided by first shutoffvalves 71 a, 71 b, and 71 c, respectively. The second connection flowpath 22 includes utilization-side second connection flow paths 22 aa, 22ab, and 22 ac and a heat source-side second connection flow path 22 b.As shown in FIG. 1, the utilization-side second connection flow paths 22aa, 22 ab, and 22 ac and the heat source-side second connection flowpath 22 b are divided by second shutoff valves 72 a, 72 b, and 72 c,respectively. The shutoff valve 70 is disposed in the refrigerantcircuit 10. The shutoff valve 70 includes the first shutoff valves 71 a,71 b, and 71 c and the second shutoff valves 72 a, 72 b, and 72 c.

Although not restrictive, the refrigerant circuit 10 is filled with aflammable refrigerant. The flammable refrigerant includes therefrigerant categorized as Class 3 (higher flammability), Class 2 (lowerflammability), and Subclass 2L (slight flammability) according to thestandards of ASHRAE 34, Designation and safety classification ofrefrigerant in the Unites States or the standards of ISO 817,Refrigerants—designation and safety classification. For example, as therefrigerant, any one of R1234yf, R1234ze(E), R516A, R445A, R444A, R454C,R444B, R454A, R455A, R457A, R459B, R452B, R454B, R447B, R32, R447A,R446A, and R459A is adopted. In the present embodiment, the refrigerantto use is R32. If R32 leaks from the refrigerant circuit 10 to the airconditioning target space (inside room) and the refrigerantconcentration in the room increases, a combustion accident may occur dueto the flammability of the refrigerant. It is required to prevent thiscombustion accident.

Note that the air conditioning system 100 and the air conditioningapparatus 1 of the present disclosure are also useful when therefrigerant is not flammable.

The configuration of the air conditioning system 100 including the airconditioning apparatus 1 will be described in detail below.

(2) Detailed Configuration

(2-1) Refrigerant Circuit

The refrigerant circuit 10 of the air conditioning apparatus 1 isdivided by the plurality of first shutoff valves 71 a, 71 b, and 71 cand the plurality of second shutoff valves 72 a, 72 b, and 72 c into aplurality of first parts 11 a, 11 b, and 11 c and a second part 12. Notethat since the first shutoff valve 71 a and the first shutoff valves 71b and 71 c have similar configurations, only the configuration of thefirst shutoff valve 71 a is described here. The description of theconfigurations of the first shutoff valves 71 b and 71 c is omitted, andinstead of the subscript “a” indicating each part of the first shutoffvalve 71 a, the subscripts “b” and “c” are added, respectively. Thesecond shutoff valves 72 a, 72 b, and 72 c and the first parts 11 a, 11b, and 11 c are described in a similar manner.

The first shutoff valve 71 a is a shutoff valve that shuts off the flowof the liquid refrigerant flowing inside the first connection flow path21 under the control of the control unit 19. The first connection flowpath 21 is divided by the first shutoff valve 71 a into theutilization-side first connection flow path 21 aa and the heatsource-side first connection flow path 21 b. The first shutoff valve 71a is connected to the liquid side of the utilization-side refrigerantflow path 13 a by the utilization-side first connection flow path 21 aa.The first shutoff valve 71 a is connected to the heat source-siderefrigerant flow path 14 by the heat source-side first connection flowpath 21 b.

The second shutoff valve 72 a is a shutoff valve that shuts off the flowof the gas refrigerant flowing inside the second connection flow path 22under the control of the control unit 19. The second connection flowpath 22 is divided by the second shutoff valve 72 a into theutilization-side second connection flow path 22 aa and the heatsource-side second connection flow path 22 b. The second shutoff valve72 a is connected to the gas side of the utilization-side refrigerantflow path 13 a by the utilization-side second connection flow path 22aa. The second shutoff valve 72 a is connected to the heat source-siderefrigerant flow path 14 by the heat source-side second connection flowpath 22 b.

The first shutoff valves 71 a, 71 b, and 71 c and the second shutoffvalves 72 a, 72 b, and 72 c may be disposed near the utilization-sideunits 3 a, 3 b, and 3 c, but may be disposed away from theutilization-side units 3 a, 3 b, and 3 c, respectively. Alternatively,as will be described in Modification E, the first shutoff valves 71 a,71 b, and 71 c and the second shutoff valves 72 a, 72 b, and 72 c may bedisposed inside a casing of the utilization-side units 3 a, 3 b, and 3c, respectively.

As shown in FIG. 1, the first parts 11 a, 11 b, and 11 c refer toutilization-side parts in the refrigerant circuit 10 divided by thefirst shutoff valves 71 a, 71 b, and 71 c and the second shutoff valves72 a, 72 b, and 72 c, respectively. The first part 11 a includes theutilization-side refrigerant flow path 13 a, the utilization-side firstconnection flow path 21 aa, and the utilization-side second connectionflow path 22 aa. The detailed configuration of the utilization-siderefrigerant flow path 13 a will be described later. The utilization-sidefirst connection flow path 21 aa is part of the first connection flowpath 21. The utilization-side first connection flow path 21 aa connectsthe utilization-side refrigerant flow path 13 a to the first shutoffvalve 71 a. The utilization-side second connection flow path 22 aa ispart of the second connection flow path 22. The utilization-side secondconnection flow path 22 aa connects the utilization-side refrigerantflow path 13 a to the second shutoff valve 72 a.

As shown in FIG. 1, the second part 12 refers to a heat source-side partin the refrigerant circuit 10 divided by the first shutoff valves 71 a,71 b, and 71 c and the second shutoff valves 72 a, 72 b, and 72 c. Thesecond part 12 includes the heat source-side refrigerant flow path 14,the heat source-side first connection flow path 21 b, and the heatsource-side second connection flow path 22 b. The detailed configurationof the heat source-side refrigerant flow path 14 will be describedlater. The heat source-side first connection flow path 21 b is part ofthe first connection flow path 21. The heat source-side first connectionflow path 21 b connects the heat source-side refrigerant flow path 14 tothe first shutoff valve 71 a. The heat source-side second connectionflow path 22 b is part of the second connection flow path 22. The heatsource-side second connection flow path 22 b connects the heatsource-side refrigerant flow path 14 to the second shutoff valve 72 a.

As will be described in detail later, if a refrigerant leakage occurs inthe first part 11 a, the control unit 19 causes the first shutoff valve71 a and the second shutoff valve 72 a to shut off the refrigerant flowbetween the first part 11 a and the second part 12. If the refrigerantflow between the first part 11 a and the second part 12 is shut off, thetotal amount of refrigerant that may flow from the first part 11 a intothe air conditioning target space is equal to the total amount ofrefrigerant filled in the first part 11 a.

The utilization-side unit 3 and the heat source-side unit 2 constitutingpart of the first part 11 a and the second part 12 will be describedbelow.

(2-2) Utilization-Side Unit

The utilization-side units 3 a, 3 b, and 3 c are installed in the airconditioning target space such as in a room of a building. As describedabove, the utilization-side refrigerant flow paths 13 a, 13 b, and 13 cof the utilization-side units 3 a, 3 b, and 3 c are connected to theheat source-side unit 2 via the first connection flow path 21, thesecond connection flow path 22, and the shutoff valve 70, andconstitutes part of the refrigerant circuit 10.

The configuration of the utilization-side units 3 a, 3 b, and 3 c willbe described. Note that since the utilization-side unit 3 a and theutilization-side units 3 b and 3 c have similar configurations, only theconfiguration of the utilization-side unit 3 a will be described here.The description of the configurations of the utilization-side units 3 band 3 c is omitted, and instead of the subscript “a” indicating eachpart of the utilization-side unit 3 a, the subscripts “b” and “c” areadded, respectively. However, the utilization-side units 3 a, 3 b, and 3c do not have to have similar configurations, and for example, thecapacity of the utilization-side units 3 a, 3 b, and 3 c may bedifferent from each other. The number of utilization-side units is notlimited to three, and may be one, two, or three or more.

The utilization-side unit 3 a mainly includes a utilization-sideexpansion valve 34 a and a utilization-side heat exchanger (heatexchanger) 30 a. Note that although detailed description is omitted, theutilization-side unit 3 a includes a casing, and various constituentdevices of the utilization-side unit 3 a are housed inside the casing ofthe utilization-side unit 3 a.

The utilization-side unit 3 a includes the utilization-side refrigerantflow path 13 a provided inside the utilization-side unit 3 a. Theutilization-side refrigerant flow path 13 a includes theutilization-side heat exchanger (heat exchanger) 30 a placed inside theutilization-side unit 3 a, the utilization-side expansion valve 34 a,and a utilization-side liquid refrigerant pipe 37 a connecting theliquid side end of the utilization-side heat exchanger (heat exchanger)30 a to the utilization-side expansion valve 34 a.

The utilization-side expansion valve 34 a is an electrically poweredexpansion valve configured to adjust the flow rate of refrigerantflowing in the utilization-side heat exchanger (heat exchanger) 30 awhile decompressing the refrigerant, and is provided in theutilization-side liquid refrigerant pipe 37 a. Note that theutilization-side expansion valve 34 a is not limited to the electricallypowered expansion valve, and may be another type of expansion valve suchas a temperature automatic expansion valve.

The utilization-side heat exchanger (heat exchanger) 30 a is a heatexchanger that functions as a refrigerant evaporator to cool indoor air,or functions as a refrigerant radiator to heat indoor air. Theutilization-side heat exchanger (heat exchanger) 30 a, which is notlimited in terms of type, is a fin-and-tube heat exchanger including aplurality of heat transfer tubes and a plurality of fins, for example.Here, the utilization-side unit 3 a includes a utilization-side fan 36a. The utilization-side fan 36 a supplies the utilization-side heatexchanger (heat exchanger) 30 a with indoor air as a cooling source or aheating source for the refrigerant flowing in the utilization-side heatexchanger (heat exchanger) 30 a. The utilization-side fan 36 a is, forexample, a centrifugal fan such as a turbo fan or a sirocco fan. Theutilization-side fan 36 a is, but is not limited to, aninverter-controlled fan, for example.

The utilization-side unit 3 a is provided with various sensors, althoughillustration is omitted. The sensors (not shown) include, but are notlimited to, a sensor that detect the temperature of the refrigerant atthe liquid side end of the utilization-side heat exchanger (heatexchanger) 30 a, a sensor that detects the temperature of therefrigerant at the gas side end of the utilization-side heat exchanger(heat exchanger) 30 a, a temperature sensor that measures thetemperature in the air conditioning target space, and the like. Theutilization-side unit 3 a is provided with a refrigerant leakage sensor50 a that detects a refrigerant leakage. The refrigerant leakage sensor50 a in the present disclosure is configured to detect the refrigeranthaving refrigerant concentration in the range of LFL/X1 to LFL/X2. Asthe refrigerant leakage sensor 50 a, for example, a semiconductor gassensor or a detection unit that detects a sharp drop in the refrigerantpressure inside the utilization-side unit 3 a can be adopted. When thesemiconductor gas sensor is used, the semiconductor gas sensor isconnected to a utilization-side control unit 93 a (see FIG. 2). When thedetection unit that detects a sharp drop in the refrigerant pressure isadopted, a pressure sensor is installed in the refrigerant pipe, and theutilization-side control unit 93 a is provided with detection algorithmto determine refrigerant leakage from a change in a value of the sensor.

Note that here, the refrigerant leakage sensor 50 a is provided in theutilization-side unit 3 a, but the present disclosure is not limited tothis example. The refrigerant leakage sensor 50 a may be provided in aremote controller for operating the utilization-side unit 3 a, in theair conditioning target space where the utilization-side unit 3 aperforms air conditioning, or the like.

(2-3) Heat Source-Side Unit

The heat source-side unit 2 is installed outside a structure such as abuilding, for example, on the roof or on the ground. As described above,the heat source-side refrigerant flow path 14 of the heat source-sideunit 2 is connected to the utilization-side units 3 a, 3 b, and 3 c viathe first connection flow path 21, the second connection flow path 22,and the shutoff valve 70, and constitutes part of the refrigerantcircuit 10.

The heat source-side unit 2 mainly includes a compressor 25, a heatsource-side heat exchanger 23, a switching mechanism 15, a first closingvalve 17 a, and a second closing valve 17 b. Note that although detaileddescription is omitted, the heat source-side unit 2 includes a casing,and various constituent devices of the heat source-side unit 2 arehoused inside the casing of the heat source-side unit 2. The switchingmechanism 15 switches between a cooling operation state in which theheat source-side heat exchanger 23 functions as a refrigerant radiatorand the utilization-side heat exchangers (heat exchangers) 30 a, 30 b,and 30 c function as refrigerant evaporators, and a heating operationstate in which the heat source-side heat exchanger 23 functions as arefrigerant evaporator and the utilization-side heat exchangers (heatexchangers) 30 a, 30 b, and 30 c function as refrigerant radiators.

The heat source-side refrigerant flow path 14 of the heat source-sideunit 2 includes, as refrigerant pipes, a suction pipe 31, a dischargepipe 32, a heat source-side first gas refrigerant pipe 33, a heatsource-side liquid refrigerant pipe 38, and a heat source-side secondgas refrigerant pipe 35 (see FIG. 1). The suction pipe 31 connects theswitching mechanism 15 to the suction side of the compressor 25. Thedischarge pipe 32 connects the discharge side of the compressor 25 tothe switching mechanism 15. The heat source-side first gas refrigerantpipe 33 connects the switching mechanism 15 to the gas side end of theheat source-side heat exchanger 23. The heat source-side liquidrefrigerant pipe 38 connects the liquid side end of the heat source-sideheat exchanger 23 to the first closing valve 17 a. A heat source-sideexpansion valve 26 is provided in the heat source-side liquidrefrigerant pipe 38. The heat source-side second gas refrigerant pipe 35connects the switching mechanism 15 to the second closing valve 17 b.

The compressor 25 sucks and compresses the low-pressure gas refrigerantin the refrigeration cycle, and discharges the high-pressure gasrefrigerant in the refrigeration cycle. The compressor 25 is, forexample, an inverter-controlled compressor. However, the compressor 25may be a constant speed compressor.

The switching mechanism 15 is a device that can switch the flow ofrefrigerant in the refrigerant circuit 10, and includes, for example, afour-way switching valve. When the heat source-side heat exchanger 23functions as a refrigerant radiator and the utilization-side heatexchangers (heat exchangers) 30 a, 30 b, and 30 c function asrefrigerant evaporators (in the cooling operation state), the switchingmechanism 15 connects the discharge side of the compressor 25 to the gasside of the heat source-side heat exchanger 23 (see the solid line ofthe switching mechanism 15 in FIG. 1). When the heat source-side heatexchanger 23 functions as a refrigerant evaporator and theutilization-side heat exchangers (heat exchangers) 30 a, 30 b, and 30 cfunction as refrigerant radiators (in the heating operation state), theswitching mechanism 15 connects the suction side of the compressor 25 tothe gas side of the heat source-side heat exchanger 23 (see the brokenline of the switching mechanism 15 in FIG. 1). Note that the switchingmechanism 15 may be implemented without using the four-way switchingvalve. For example, the switching mechanism 15 may be configured bycombining a plurality of electromagnetic valves and pipes so as toimplement switching of the refrigerant flow direction as describedabove.

The heat source-side heat exchanger 23 is a heat exchanger thatfunctions as a refrigerant radiator or functions as a refrigerantevaporator. The heat source-side heat exchanger 23 is, but is notlimited to, a fin-and-tube heat exchanger including a plurality of heattransfer tubes and a plurality of heat transfer fins, for example. Here,the heat source-side unit 2 includes a heat source-side fan 24. The heatsource-side fan 24 sucks outdoor air into the heat source-side unit 2,causes the sucked outdoor air to exchange heat with the refrigerant inthe heat source-side heat exchanger 23, and discharges the air to theoutside. The heat source-side fan 24 is driven by a heat source-side fanmotor. The heat source-side fan 24 is, for example, aninverter-controlled fan. However, the heat source-side fan 24 may be aconstant speed fan.

In the cooling operation, the air conditioning apparatus 1 of the airconditioning system 100 causes the refrigerant to flow from the heatsource-side heat exchanger 23 to the utilization-side heat exchangers(heat exchangers) 30 a, 30 b, and 30 c, each functioning as arefrigerant evaporator, through the first connection flow path 21. Inthe heating operation, the air conditioning apparatus 1 causes therefrigerant to flow from the compressor 25 to the utilization-side heatexchangers (heat exchangers) 30 a, 30 b, and 30 c, each functioning as arefrigerant radiator, through the second connection flow path 22. In thecooling operation, the switching mechanism 15 switches to the coolingoperation state, the heat source-side heat exchanger 23 functions as arefrigerant radiator, and the refrigerant flows from the heatsource-side unit 2 side to the utilization-side units 3 a, 3 b, and 3 cside through the first connection flow path 21. In the heatingoperation, the switching mechanism 15 switches to the heating operationstate, the refrigerant flows from the utilization-side units 3 a, 3 b,and 3 c side to the heat source-side unit 2 side through the firstconnection flow path 21, and the heat source-side heat exchanger 23functions as a refrigerant evaporator.

Here, the heat source-side liquid refrigerant pipe 38 is provided withthe heat source-side expansion valve 26. The heat source-side expansionvalve 26 is an electrically powered expansion valve configured todecompress the refrigerant in the heating operation, and is provided ata portion near the liquid side end of the heat source-side heatexchanger 23 in the heat source-side liquid refrigerant pipe 38. Notethat the heat source-side expansion valve 26 is not limited to theelectrically powered expansion valve, and may be another type ofexpansion valve such as a temperature automatic expansion valve.

The heat source-side unit 2 is provided with various sensors, althoughillustration is omitted. The sensors provided in the heat source-sideunit 2 include, but are not limited to, a temperature sensor and apressure sensor placed in the suction pipe 31 and the discharge pipe 32,a temperature sensor placed in the heat source-side heat exchanger 23and the heat source-side liquid refrigerant pipe 38, a temperaturesensor for measuring the temperature of heat source air, and the like.However, the heat source-side unit 2 does not have to include all ofthese sensors.

(2-4) Control Unit

The control unit 19 is configured by connecting a heat source-sidecontrol unit 92 to the utilization-side control units 93 a, 93 b, and 93c via a transmission line 90, as shown in FIG. 2. The heat source-sidecontrol unit 92 controls constituent devices of the heat source-sideunit 2. The utilization-side control units 93 a, 93 b, and 93 c controlconstituent devices of the utilization-side units 3 a, 3 b, and 3 c, thefirst shutoff valves 71 a, 71 b, and 71 c, and the second shutoff valves72 a, 72 b, and 72 c, respectively. The heat source-side control unit 92included in the heat source-side unit 2, and the utilization-sidecontrol units 93 a, 93 b, and 93 c included in the utilization-sideunits 3 a, 3 b, and 3 c exchange information such as control signalswith one another via the transmission line 90.

The heat source-side control unit 92 includes a control board on whichelectrical components such as a microcomputer and a memory are mounted,and is connected to, for example, various constituent devices 15, 17 a,17 b, 23, 24, 25, 26 of the heat source-side unit 2, various sensors(not shown), and the like. The utilization-side control units 93 a, 93b, and 93 c each include a control board on which electrical componentssuch as a microcomputer and a memory are mounted, and for example,various constituent devices 30 a, 30 b, 30 c, 34 a, 34 b, 34 c, 36 a, 36b, 36 c of the utilization-side units 3 a, 3 b, and 3 c, various shutoffvalves 71 a, 71 b, 71 c, 72 a, 72 b, and 72 c, refrigerant leakagesensors 50 a, 50 b, and 50 c, various sensors (not shown), and the likeare connected.

In this way, the control unit 19 controls the operation of the entireair conditioning apparatus 1. Specifically, based on detection signalsof various sensors (not shown) as described above, the refrigerantleakage sensors 50 a, 50 b, and 50 c, and the like, the control unit 19controls various constituent devices 15, 17 a, 17 b, 23, 24, 25, 26, 30a, 30 b, 30 c, 34 a, 34 b, 34 c, 36 a, 36 b, 36 c, 71 a, 71 b, 71 c, 72a, 72 b, and 72 c of the air conditioning apparatus 1.

(3) Operation of Air Conditioning Apparatus when Refrigerant Leaks

Next, the operation of the air conditioning apparatus 1 when arefrigerant leaks will be described with reference to FIG. 3. In asimilar manner to the basic operation described above, the operation ofthe air conditioning apparatus 1 described below when a refrigerantleaks is performed by the control unit 19 that controls the constituentdevices of the air conditioning apparatus 1.

Since similar control is performed even if the refrigerant leaks in anyof the first parts 11 a, 11 b, and 11 c, the case where the refrigerantleakage is detected in the first part 11 a will be described here as anexample.

In step S1 of FIG. 3, it is determined whether any of the refrigerantleakage sensors 50 a, 50 b, and 50 c of the utilization-side units 3 a,3 b, and 3 c has detected a refrigerant leakage. Here, when therefrigerant leakage sensor 50 a of the utilization-side unit 3 a detectsthe refrigerant leakage in the first part 11 a, the process proceeds tonext step S2.

In step S2, in the first part 11 a where the refrigerant leaks, an alarmis issued to a person in the space where the utilization-side unit 3 ais installed (air conditioning target space) by using an alarm device(not shown) that issues an alarm with an alarm sound such as a buzzerand turns on light.

Next, in step S3, the first shutoff valve 71 a and the second shutoffvalve 72 a, which are shutoff valves corresponding to the first part 11a where the refrigerant leaks, are closed. Accordingly, the upstreamside and the downstream side of the first shutoff valve 71 a and thesecond shutoff valve 72 a are separated from each other, and therefrigerant flow between the first part 11 a and the second part 12discontinues. As a result, the inflow of refrigerant from the secondpart 12 or the first parts 11 b and 11 c to the first part 11 adiscontinues.

(4) Method of Determining Position to Place Refrigerant Shutoff Valve

(4-1)

If the refrigerant leaks in the first part 11 a, all the refrigerantfilled in the refrigerant circuit 10 may leak to the air conditioningtarget space. Therefore, when the refrigerant leakage sensor 50 adetects the refrigerant leakage, the control unit 19 shuts off the firstshutoff valve 71 a and the second shutoff valve 72 a. Since therefrigerant flow between the first part 11 a and the second part 12 isshut off accordingly, all the refrigerant filled in the refrigerantcircuit 10 is prevented from leaking to the air conditioning targetspace. In this case, the total amount of refrigerant contained in thefirst part 11 a is the total amount of refrigerant considered to leak tothe air conditioning target space. The maximum value of the total amountof refrigerant contained in the first part 11 a can be calculated fromthe volume of the utilization-side refrigerant flow path 13 a, thevolume of the utilization-side first connection flow path 21 aa, and thevolume of the utilization-side second connection flow path 22 aa. As thevolume of the utilization-side refrigerant flow path 13 a, the volume ofthe utilization-side first connection flow path 21 aa, and the volume ofthe utilization-side second connection flow path 22 aa increase, themaximum value of the total amount of refrigerant contained in the firstpart 11 a increases.

If the amount of refrigerant contained in the first part 11 a is largeand the volume of the air conditioning target space is small, therefrigerant concentration of the refrigerant leaked to the airconditioning target space may be large. In other words, if the volume ofthe utilization-side refrigerant flow path 13 a, the volume of theutilization-side first connection flow path 21 aa, and the volume of theutilization-side second connection flow path 22 aa are large, and if thevolume of the air conditioning target space is small, the refrigerantconcentration of the refrigerant R32 near the floor of the airconditioning target space may become large and exceed the LFL/safetyfactor. Note that the lower flammability limit (LFL) is minimumrefrigerant concentration specified by ISO 817 and enabling flamepropagation in a state where a refrigerant and air are mixed uniformly.Therefore, the first shutoff valve 71 a and the second shutoff valve 72a need to be placed at positions where there is no risk of exceeding theLFL/safety factor of the air conditioning target space even if all therefrigerant present in the first part 11 a leaks to the air conditioningtarget space.

(4-2) Second Range

The refrigerant circuit 10 of the air conditioning apparatus 1 isdivided by the first shutoff valve 71 a and the second shutoff valve 72a into the first part 11 a and the second part 12. The first part 11 aincludes the utilization-side refrigerant flow path 13 a, theutilization-side first connection flow path 21 aa, and theutilization-side second connection flow path 22 aa. The total amount ofrefrigerant contained in the first part 11 a is the total amount ofrefrigerant that is considered to leak to the air conditioning targetspace. The maximum value of the total amount of refrigerant contained inthe first part 11 a can be calculated from the volume of theutilization-side refrigerant flow path 13 a, the volume of theutilization-side first connection flow path 21 aa, and the volume of theutilization-side second connection flow path 22 aa. In other words, themaximum value of the total amount of refrigerant contained in the firstpart 11 a changes depending on the positions where the first shutoffvalve 71 a and the second shutoff valve 72 a are placed in therefrigerant circuit 10. For example, when the first shutoff valve 71 aand the second shutoff valve 72 a are placed away from the position ofthe utilization-side unit 3 a in the refrigerant circuit 10, the volumeof the utilization-side first connection flow path 21 aa and the volumeof the utilization-side second connection flow path 22 aa are large, andtherefore the maximum value of the total amount of refrigerant containedin the first part 11 a is large.

If a refrigerant leakage occurs in the first part 11 a, the refrigerantconcentration of the refrigerant leaked to the air conditioning targetspace changes depending on the positions where the first shutoff valve71 a and the second shutoff valve 72 a are placed in the refrigerantcircuit 10. In the present disclosure, the first shutoff valve 71 a andthe second shutoff valve 72 a are placed at positions where therefrigerant concentration in the air conditioning target space is withinthe second range when it is assumed that all the refrigerant present inthe first part 11 a at a predetermined temperature, a predeterminedpressure, and a predetermined phase state leaks to the air conditioningtarget space. The second range is a range of refrigerant concentrationin which it is considered that the occurrence of combustion accidentcaused by the refrigerant leakage in the air conditioning target spacecan be inhibited. The second range is from LFL/Y1 to LFL/Y2. Y1 and Y2are safety factors. When the second range is B, the second range is, butis not limited to, LFL/100<B<LFL/1, for example. Even if the refrigerantleakage occurs in the first part 11 a and the refrigerant leaks to theair conditioning target space, the occurrence of combustion accident isinhibited when the refrigerant concentration in the air conditioningtarget space is within the second range.

(4-3) First Range

As described above, if the refrigerant leakage occurs in the first part11 a, after the refrigerant leakage sensor 50 a detects the refrigerantleakage, the control unit 19 causes the first shutoff valve 71 a and thesecond shutoff valve 72 a to shut off the flow of refrigerant betweenthe first part 11 a and the second part 12. In other words, only afterthe refrigerant leakage sensor 50 a detects the refrigerant leakage, thecontrol unit 19 can cause the first shutoff valve 71 a and the secondshutoff valve 72 a to shut off the flow of refrigerant between the firstpart 11 a and the second part 12.

Therefore, if the refrigerant concentration that can be detected by therefrigerant leakage sensor 50 a is larger than concentration in thesecond range, it is considered that an amount of refrigerant exceedingthe second range leaks from the first part 11 a to the air conditioningtarget space before the first shutoff valve 71 a and the second shutoffvalve 72 a shut off the flow between the first part 11 a and the secondpart 12.

In view of the above-described circumstances, the refrigerant leakagesensor 50 a is configured to detect the refrigerant having refrigerantconcentration in the first range smaller than the refrigerantconcentration in the second range. The first range is from LFL/X1 toLFL/X2. X1 and X2 are safety factors. When the first range is A, thefirst range is, but is not limited to, LFL/100≤A≤LFL/4, for example.

In general, combustion accidents in the air conditioning target spacecaused by a refrigerant leakage occur because a large amount ofrefrigerant that exceeds the lower limit concentration of combustion inthe air conditioning target space leaks to the air conditioning targetspace. The refrigerant leakage sensor 50 a in the present disclosure candetect the refrigerant having refrigerant concentration within the firstrange. The refrigerant concentration of the refrigerant in the firstrange is smaller than the refrigerant concentration of the refrigerantin the second range. In other words, the refrigerant leakage sensor 50 acan detect even a refrigerant having small (thin) refrigerantconcentration. This allows the control unit 19 to control the firstshutoff valve 71 a and the second shutoff valve 72 a such that therefrigerant concentration in the air conditioning target space is withinthe second range after the refrigerant leakage sensor 50 a detects therefrigerant leakage.

(4-4) Relationship Between First Range and Second Range

As described above, the second range is a range of refrigerantconcentration in which it is considered that the occurrence ofcombustion accident caused by the refrigerant leakage in the airconditioning target space can be inhibited. As described above, if therefrigerant leakage sensor 50 a cannot detect the refrigerant havingrefrigerant concentration in the second range, the refrigerant exceedingthe second range may leak to the air conditioning target space.

Therefore, in the present disclosure, it is determined that X1 for thefirst range is larger than Y1 for the second range, and that X2 for thefirst range is larger than Y2 for the second range. In other words, thenumerical value to be substituted for X1 for the first range is largerthan the numerical value to be substituted for Y1 for the second range,and the numerical value to be substituted for X2 for the first range islarger than the numerical value to be substituted for Y2 for the secondrange. For example, if the safety factor X1 for the first range is 50and the safety factor X2 is 4, the safety factor Y1 for the second rangeis, for example, 49, and the safety factor Y2 is, for example, 1. Inthis way, the refrigerant concentration in the first range is definitelysmaller than the refrigerant concentration in the second range, and therefrigerant leakage sensor 50 a can detect the refrigerant leakagebefore the amount of refrigerant exceeding the second range leaks to theair conditioning target space.

X1 being larger than Y1 and X2 being larger than Y2 mean that, in otherwords, LFL/Y1 is refrigerant concentration larger than LFL/X1, andLFL/Y2 is refrigerant concentration larger than LFL/X2. In other wordsagain, this means that LFL/Y1 is darker in refrigerant concentrationthan LFL/X1, and LFL/Y2 is darker in refrigerant concentration thanLFL/X2. Therefore, if the first range is A and the second range is B, itcan be said that the first range and the second range are ranges thatsatisfy the following formulas.

LFL/100≤A≤LFL/4  (Formula 1):

LFL/100<B<LFL/1  (Formula 2):

When A and B satisfy Formulas 1 and 2, the refrigerant leakage sensor 50a can detect the refrigerant in the second range.

(4-5) Method of Determining Position to Place Refrigerant Shutoff Valve

According to what has been described above, one example of the method ofdetermining the position to place the first shutoff valve 71 a and thesecond shutoff valve 72 a in the refrigerant circuit 10 will bedescribed. Although not restrictive, to begin with, the second range isdetermined, which is a range of refrigerant concentration in which it isconsidered to be possible to inhibit the occurrence of combustionaccident caused by a refrigerant leakage in the air conditioning targetspace when the refrigerant leakage occurs from the first part 11 a.Next, the first range, which is a range of refrigerant concentrationthat can be detected by the refrigerant leakage sensor 50 a, isdetermined. At this time, in order to allow the refrigerant leakagesensor 50 a to reliably detect the refrigerant having refrigerantconcentration in the second range, the refrigerant concentration in thefirst range is set smaller than the refrigerant concentration in thesecond range. Finally, the first shutoff valve 71 a and the secondshutoff valve 72 a are placed at positions where the refrigerant leakedto the air conditioning target space is within the second range even ifthe refrigerant leakage occurs in the first part 11 a. As the positionswhere the first shutoff valve 71 a and the second shutoff valve 72 a areplaced move away from the utilization-side unit 3 a, the volume of theutilization-side first connection flow path 21 aa and the volume of theutilization-side second connection flow path 22 aa will increase, andtherefore an amount of refrigerant that can exceed the second range maybe contained in the first part 11 a. Therefore, the first shutoff valve71 a and the second shutoff valve 72 a are placed based on the volume ofthe utilization-side refrigerant flow path 13 a, the volume of theutilization-side first connection flow path 21 aa, the volume of theutilization-side second connection flow path 22 aa, and the volume ofthe air conditioning target space. In this way, the positions to placethe first shutoff valve 71 a and the second shutoff valve 72 a in therefrigerant circuit 10 are determined.

The method of determining the positions to place the first shutoff valve71 a and the second shutoff valve 72 a in the refrigerant circuit 10 isnot limited to the above method, and the first range may be determinedfirst. For example, as the refrigerant leakage sensor 50 a, therefrigerant leakage sensor 50 a capable of detecting certainconcentration in the first range is determined. Next, the second rangeis determined such that the refrigerant concentration in the secondrange is larger (higher) than the refrigerant concentration in the firstrange. This allows the refrigerant leakage sensor 50 a to detect arefrigerant smaller (thinner) than the second range. Finally, the firstshutoff valve 71 a and the second shutoff valve 72 a are placed atpositions where the refrigerant leaked to the air conditioning targetspace is within the second range even if the refrigerant leakage occursin the first part 11 a. The upper limit of the second range is a valuesmaller than LFL/1.

(5) Features

(5-1)

The air conditioning system 100 of the first aspect includes therefrigerant circuit 10, the heat exchangers 30 a, 30 b, and 30 c, theshutoff valve 70, and the refrigerant leakage sensors 50 a, 50 b, and 50c. The refrigerant circuit 10 includes the first parts 11 a, 11 b, and11 c and the second part 12. The heat exchangers 30 a, 30 b, and 30 care provided in the first parts 11 a, 11 b, and 11 c, respectively, andcool or heat the air in the air conditioning target space by exchangingheat between the refrigerant and the air in the air conditioning targetspace. The shutoff valve 70 is provided in the refrigerant circuit 10and shuts off communication between the first parts 11 a, 11 b, and 11 cand the second part 12. The refrigerant leakage sensors 50 a, 50 b, and50 c detect the refrigerant leaked from the first parts 11 a, 11 b, and11 c, respectively. The refrigerant leakage sensors 50 a, 50 b, and 50 cdetect that the refrigerant concentration is within the first range. Theshutoff valve 70 is placed such that the refrigerant concentration inthe air conditioning target space is within the second range, which is arange larger than the first range, when it is assumed that all therefrigerant present in the first parts 11 a, 11 b, and 11 c has leakedto the air conditioning target space.

In the air conditioning system 100 of the first aspect, the shutoffvalve 70 is placed at a position where the refrigerant concentration inthe air conditioning target space is within the second range, forexample, even if all the refrigerant present in the first part 11 aleaks to the air conditioning target space. This inhibits therefrigerant concentration in the air conditioning target space fromexceeding LFL (Lower Flammability Limit).

Furthermore, in the air conditioning system 100 of the first aspect, therefrigerant concentration in the second range is larger than therefrigerant concentration in the first range. Accordingly, for example,if a refrigerant leakage occurs in the first part 11 a, an amount ofrefrigerant exceeding the LFL/safety factor in the air conditioningtarget space is inhibited from leaking from the first part 11 a beforethe shutoff valve 70 shuts off the flow between the first part 11 a andthe second part 12.

(5-2)

The air conditioning system 100 of the second aspect is the airconditioning system 100 of the first aspect, in which when the lowerlimit concentration of refrigerant combustion is LFL (Lower FlammabilityLimit) [kg/m³], the first range is from LFL/X1 to LFL/X2 and the secondrange is from LFL/Y1 to LFL/Y2. X1 is larger than Y1, and X2 is largerthan Y2.

The air conditioning system 100 of the second aspect sets the firstrange and the second range such that the refrigerant concentration issmaller than LFL in the air conditioning target space. This inhibits therefrigerant concentration in the air conditioning target space fromexceeding LFL.

Note that X1 being larger than Y1 and X2 being larger than Y2 mean that,in other words, LFL/Y1 is larger than LFL/X1, and LFL/Y2 is larger thanLFL/X2.

Note that the first range being from LFL/X1 to LFL/X2 means that, inother words, if the first range is A, LFL/X1≤A≤LFL/X2.

Note that the second range being from LFL/Y1 to LFL/Y2 means that, inother words, if the second range is B, LFL/Y1<B<LFL/Y2.

(5-3)

The air conditioning system 100 of the third aspect is the airconditioning system 100 of the first aspect or the second aspect, inwhich the refrigerant circuit 10 includes the utilization-siderefrigerant flow paths 13 a, 13 b, and 13 c, which are part of the firstparts 11 a, 11 b, and 11 c, the heat source-side refrigerant flow path14, which is part of the second part 12, and the first connection flowpath 21 and the second connection flow path 22 connecting theutilization-side refrigerant flow paths 13 a, 13 b, and 13 c to the heatsource-side refrigerant flow path 14. The shutoff valve 70 includes thefirst shutoff valves 71 a, 71 b, and 71 c provided in the firstconnection flow path 21 and the second shutoff valves 72 a, 72 b, and 72c provided in the second connection flow path 22. The first connectionflow path 21 includes the utilization-side first connection flow paths21 aa, 2 lab, and 21 ac between the utilization-side refrigerant flowpaths 13 a, 13 b, and 13 c and the first shutoff valves 71 a, 71 b, and71 c, and the heat source-side first connection flow path 21 b betweenthe heat source-side refrigerant flow path 14 and the first shutoffvalves 71 a, 71 b, and 71 c. The second connection flow path 22 includesthe utilization-side second connection flow paths 22 aa, 22 ab, and 22ac between the utilization-side refrigerant flow paths 13 a, 13 b, and13 c and the second shutoff valves 72 a, 72 b, and 72 c, and the heatsource-side second connection flow path 22 b between the heatsource-side refrigerant flow path 14 and the second shutoff valves 72 a,72 b, and 72 c. The first shutoff valves 71 a, 71 b, and 71 c and thesecond shutoff valves 72 a, 72 b, and 72 c are placed based on thevolume of the utilization-side refrigerant flow paths 13 a, 13 b, and 13c, the volume of the utilization-side first connection flow paths 21 aa,21 ab, and 21 ac, the volume of the utilization-side second connectionflow paths 22 aa, 22 ab, and 22 ac, and the volume of the airconditioning target space.

In the air conditioning system 100 of the third aspect, the firstshutoff valves 71 a, 71 b, and 71 c and the second shutoff valves 72 a,72 b, and 72 c are placed based on the volume of the utilization-siderefrigerant flow paths 13 a, 13 b, and 13 c, the volume of theutilization-side first connection flow paths 21 aa, 21 ab, and 21 ac,the volume of the utilization-side second connection flow paths 22 aa,22 ab, and 22 ac, and the volume of the air conditioning target space.This inhibits the refrigerant concentration in the air conditioningtarget space from exceeding LFL.

(5-4)

The air conditioning system 100 of the fourth aspect is the airconditioning system 100 of the first aspect, in which when the lowerlimit concentration of refrigerant combustion is LFL [kg/m³], the firstrange is from LFL/X1 to LFL/X2 and the second range is from LFL/Y1 toLFL/Y2. LFL/Y1 is larger than LFL/X1, and LFL/Y2 is larger than LFL/X2.

The air conditioning system 100 of the fourth aspect sets the firstrange and the second range such that the refrigerant concentration issmaller than LFL in the air conditioning target space. This inhibits therefrigerant concentration in the air conditioning target space fromexceeding LFL.

Note that the first range being from LFL/X1 to LFL/X2 means that, inother words, if the first range is A, LFL/X1≤A≤LFL/X2.

The second range being from LFL/Y1 to LFL/Y2 means that, in other words,if the second range is B, LFL/Y1<B<LFL/Y2.

(6) Modifications

The above-described embodiment can be appropriately modified as shown inthe following modifications. Each modification may be applied incombination with other modifications insofar as no inconsistency arises.Note that constituent elements similar to those described in the firstembodiment are denoted with similar reference signs, and the detaileddescription thereof will be omitted.

(6-1) Modification A

The above-described embodiment has described an example in which thefirst shutoff valves 71 a, 71 b, and 71 c and the second shutoff valves72 a, 72 b, and 72 c are placed in the refrigerant circuit 10 so as tocorrespond to the utilization-side units 3 a, 3 b, and 3 c,respectively. However, if the above-described shutoff valves are placedat positions where the refrigerant concentration in the air conditioningtarget space is within the second range when it is assumed that all therefrigerant present in a first part 11A at a predetermined temperature,predetermined pressure, and predetermined phase state has leaked to theair conditioning target space, as shown in FIG. 4, one first shutoffvalve 71A and one second shutoff valve 72A may be connected to each ofthe plurality of utilization-side units 3 a, 3 b, and 3 c.

In this case, as shown in FIG. 4, the first part 11A includes theutilization-side refrigerant flow path 13 a, the utilization-siderefrigerant flow path 13 b, the utilization-side refrigerant flow path13 c, the utilization-side liquid refrigerant pipe 37 a, theutilization-side liquid refrigerant pipe 37 b, the utilization-sideliquid refrigerant pipe 37 c, a utilization-side first connection flowpath 21A, and a utilization-side second connection flow path 22A. Thefirst connection flow path 21 includes the utilization-side firstconnection flow path 21A and the heat source-side first connection flowpath 21 b. The second connection flow path 22 includes theutilization-side second connection flow path 22A and the heatsource-side second connection flow path 22 b. Note that theconfiguration of the first shutoff valve 71A and the second shutoffvalve 72A is similar to the configuration of the first shutoff valves 71a, 71 b, and 71 c and the second shutoff valves 72 a, 72 b, and 72 c,and thus the description thereof will be omitted.

Note that in FIG. 4, the utilization-side control unit 93 a is connectedto the first shutoff valve 71A and the second shutoff valve 72A, butthis is not restrictive. The utilization-side control unit 93 b or theutilization-side control unit 93 c may be connected to the first shutoffvalve 71A and the second shutoff valve 72A.

FIG. 4 illustrates the utilization-side units 3 a, 3 b, and 3 c, but thenumber of utilization-side units is not limited to this example, and maybe three or less, or three or more.

(6-2) Modification B

The above-described embodiment has described an example in which thefirst shutoff valves 71 a, 71 b, and 71 c and the second shutoff valves72 a, 72 b, and 72 c are placed corresponding to the threeutilization-side units 3 a, 3 b, and 3 c. However, the number ofutilization-side units is not limited to three, and the number of firstshutoff valves and the second shutoff valves is not limited to three.For example, as shown in FIG. 5, one utilization-side unit 3S may beconnected to the heat source-side unit 2 by the first connection flowpath 21 and the second connection flow path 22 via one first shutoffvalve 71S and one second shutoff valve 72S.

In this case, as shown in FIG. 5, a first part 11S includes autilization-side refrigerant flow path 13S, a utilization-side liquidrefrigerant pipe 37S, a utilization-side first connection flow path 21S,and a utilization-side second connection flow path 22S. The firstconnection flow path 21 includes the utilization-side first connectionflow path 21S and the heat source-side first connection flow path 21 b.The second connection flow path 22 includes the utilization-side secondconnection flow path 22S and the heat source-side second connection flowpath 22 b.

Note that the configuration of constituent devices 30S, 34S, 36S, 37S,50S, and 92S of the utilization-side unit 3S is similar to theconfiguration of various constituent devices 30 a, 30 b, 30 c, 34 a, 34b, 34 c, 36 a, 36 b, 36 c, 37 a, 37 b, 37 c, 50 a, 50 b, 50 c, 92 a, 92b, and 92 c of the utilization-side units 3 a, 3 b, and 3 c, and thusthe description thereof will be omitted. The configuration of theutilization-side refrigerant flow path 13S is similar to theconfiguration of the utilization-side refrigerant flow paths 13 a, 13 b,and 13 c, and thus the description thereof will be omitted.

(6-3) Modification C

The above-described embodiment has described that the utilization-sidecontrol units 93 a, 93 b, and 93 c control the first shutoff valves 71a, 71 b, and 71 c and the second shutoff valves 72 a, 72 b, and 72 c,respectively. However, the heat source-side control unit 92 may controlthe first shutoff valves 71 a, 71 b, and 71 c and the second shutoffvalves 72 a, 72 b, and 72 c.

(6-4) Modification D

The above-described embodiment has described that the control unit 19 isconfigured by connecting the heat source-side control unit 92 to theutilization-side control units 93 a, 93 b, and 93 c via the transmissionline 90. However, the heat source-side control unit 92 or theutilization-side control units 93 a, 93 b, and 93 c may control theoperation of the entire air conditioning apparatus 1. For example, theheat source-side control unit 92 may control various constituent devices15, 17 a, 17 b, 23, 24, 25, 26, 30 a, 30 b, 30 c, 34 a, 34 b, 34 c, 36a, 36 b, 36 c, 71 a, 71 b, 71 c, 72 a, 72 b, and 72 c of the airconditioning apparatus 1 based on detection signals of various sensors(not shown), the refrigerant leakage sensors 50 a, 50 b, and 50 c, andthe like.

(6-5) Modification E

The above-described embodiment has described an example in which thefirst shutoff valves 71 a, 71 b, and 71 c and the second shutoff valves72 a, 72 b, and 72 c are placed outside the utilization-side units 3 a,3 b, and 3 c and the heat source-side unit 2. However, as shown in FIG.6, the utilization-side unit 3 a may include the first shutoff valves 71a, 71 b, and 71 c and the second shutoff valves 72 a, 72 b, and 72 cinside the utilization-side units 3 a, 3 b, and 3 c, by placement insidethe casing of the utilization-side units 3 a, 3 b, and 3 c. The firstshutoff valves 71 a, 71 b, and 71 c and the second shutoff valves 72 a,72 b, and 72 c placed inside the casing may be controlled by, forexample, the utilization-side control units 93 a, 93 b, and 93 c,although not restrictive.

<Supplementary Note>

The embodiment of the present disclosure has been described above. Itwill be understood that various changes to modes and details can be madewithout departing from the spirit and scope of the present disclosurerecited in the claims.

REFERENCE SIGNS LIST

-   -   10: refrigerant circuit    -   11 a, 11 b, 11 c, 11A, 11S: first part    -   12: second part    -   13 a, 13 b, 13 c, 13S: utilization-side refrigerant flow path    -   14: heat source-side refrigerant flow path    -   21: first connection flow path    -   22: second connection flow path    -   21 aa, 21 ab, 21 ac, 21A, 21S: utilization-side first connection        flow path    -   21 b: heat source-side first connection flow path    -   22 aa, 22 ab, 22 ac, 21A, 21S: utilization-side second        connection flow path    -   22 b: heat source-side second connection flow path    -   30 a, 30 b, 30 c, 30S: heat exchanger    -   50 a, 50 b, 50 c, 50S: refrigerant leakage sensor    -   70: shutoff valve (first shutoff valve, second shutoff valve)    -   71 a, 71 b, 71 c, 71A, 71S: first shutoff valve    -   72 a, 72 b, 72 c, 72A, 72S: second shutoff valve    -   100: air conditioning system

CITATION LIST Patent Literature

-   Patent Literature 1: Japanese Laid-Open Patent Publication No.    2019-45129

1. An air conditioning system comprising: a refrigerant circuitincluding a first part and a second part; a heat exchanger provided inthe first part and configured to cool or heat air in an air conditioningtarget space by exchanging heat between a refrigerant and the air in theair conditioning target space; a shutoff valve provided in therefrigerant circuit and configured to shut off communication between thefirst part and the second part; and a refrigerant leakage sensorconfigured to detect the refrigerant leaked from the first part, whereinthe refrigerant leakage sensor detects that refrigerant concentration iswithin a first range, and the shutoff valve is placed to set therefrigerant concentration in the air conditioning target space within asecond range that is a range larger than the first range when it isassumed that all the refrigerant present in the first part has leaked tothe air conditioning target space.
 2. The air conditioning systemaccording to claim 1, wherein when a lower limit concentration ofcombustion of the refrigerant is LFL [kg/m³], the first range is fromLFL/X1 to LFL/X2, the second range is from LFL/Y1 to LFL/Y2, and X1 islarger than Y1, and X2 is larger than Y2.
 3. The air conditioning systemaccording to claim 1, wherein the refrigerant circuit includes autilization-side refrigerant flow path that is part of the first part, aheat source-side refrigerant flow path that is part of the second part,and a first connection flow path and a second connection flow pathconnecting the utilization-side refrigerant flow path to the heatsource-side refrigerant flow path, the shutoff valve includes a firstshutoff valve provided in the first connection flow path and a secondshutoff valve provided in the second connection flow path, the firstconnection flow path includes a utilization-side first connection flowpath between the utilization-side refrigerant flow path and the firstshutoff valve, and a heat source-side first connection flow path betweenthe heat source-side refrigerant flow path and the first shutoff valve,the second connection flow path includes a utilization-side secondconnection flow path between the utilization-side refrigerant flow pathand the second shutoff valve, and a heat source-side second connectionflow path between the heat source-side refrigerant flow path and thesecond shutoff valve, and the first shutoff valve and the second shutoffvalve are placed based on volume of the utilization-side refrigerantflow path, volume of the utilization-side first connection flow path,volume of the utilization-side second connection flow path, and volumeof the air conditioning target space.
 4. The air conditioning systemaccording to claim 2, wherein the refrigerant circuit includes autilization-side refrigerant flow path that is part of the first part, aheat source-side refrigerant flow path that is part of the second part,and a first connection flow path and a second connection flow pathconnecting the utilization-side refrigerant flow path to the heatsource-side refrigerant flow path, the shutoff valve includes a firstshutoff valve provided in the first connection flow path and a secondshutoff valve provided in the second connection flow path, the firstconnection flow path includes a utilization-side first connection flowpath between the utilization-side refrigerant flow path and the firstshutoff valve, and a heat source-side first connection flow path betweenthe heat source-side refrigerant flow path and the first shutoff valve,the second connection flow path includes a utilization-side secondconnection flow path between the utilization-side refrigerant flow pathand the second shutoff valve, and a heat source-side second connectionflow path between the heat source-side refrigerant flow path and thesecond shutoff valve, and the first shutoff valve and the second shutoffvalve are placed based on volume of the utilization-side refrigerantflow path, volume of the utilization-side first connection flow path,volume of the utilization-side second connection flow path, and volumeof the air conditioning target space.